Synthesizes 6 hormones hypothalamus secretes

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- Synthesizes 6 hormones - Hypothalamus secretes releasing hormones which flow through the blood to the anterior pituitary 2) Posterior Pituitary Gland –Composed of neural tissue, can be considered as extension of hypothalamus - Neurons in the hypothalamus synthesize hormones oxytocin and vasopressin which migrate down axons to the posterior gland, later to be released by gland into blood - RECAP: The posterior pituitary is neural tissue, like the hypothalamus. The anterior pituitary is glandular tissue and produces hormones that control several other endocrine organs - Most NT's are released in small amounts close to their receptors. Neuropeptides are releasedinto a brain area in larger amounts or not at all. When released, they diffuse more widely. Hormones are released into the blood for diffuse delivery throughout the bodyInactivation and Reuptake of NT's - After ACH acetylcholine activates a receptor, it is broken down by the enzyme acetylcholinestereaseinto two fragments 1) Acetate - 2) Choline – Choline diffuses back to the presynaptic neuron, recycling it - Serotonin and the catecholamines (dopamine, norepinephrine, epinephrine) do not break downinto inactive fragments at the postsynaptic membrane – they simply detach from the receptor then they take 1 of 2 processes:1) Reuptake: Presynaptic neuron takes up most of the released NT and and reuses themOccurs through special membrane proteins called 'transporters' - Dopamine transporters in the caudate nucleus are highly efficient and reuptake accounts for nearly all of the released dopamine- In other brain areas, fewer transporters are present and reuptake is slower, if dopamine releases rapidly in those areas, it accumulates and an enzyme called COMT breaksdown the excess into inactive chemicals that cannot stimulate dopamine receptors - In the prefrontal cortex,COMT breaks down about half of it's released dopamine - Neuropeptides are neither inactivated nor reabsorbed they simply diffuse away - RECAP: The enzyme acetylcholinesterase breaks acetylcholine molecules into two smaller molecules, acetate and choline, which are then reabsorbed be the presynaptic terminal - Most serontonin and catecholamine molecules are reabsorbed by the presynaptic terminalSome are broken down into inactive chemicals which then diffuse away Negative Feedback from the Postsynaptic Cell - The “yes I got your message, don't send it again' mechanisms - Autoreceptors: Presynaptic Receptors that respond to the released transmitter by inhibiting further synthesis and release – this provided negative feedback - Postsynaptic neurons respond to stimulation by releasing special chemicals that travel back to the presynaptic terminal, where they inhibit further release of the NT – Nitric oxide is one - Also 'Anandamide' and 2-AG
Electrical Synapses - Faster than any other synapse- Rhythmic breathing is controlled by electrical synapse - The membrane of one neuron comes into direct contact with the membrane of another neuron, called a Gap Junction with channels that constantly remain open

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